In the process of manufacturing ICs with LSI, VLSI and ULSI, patterned material layers like patterned photoresist layers, patterned barrier material layers containing or consisting of titanium nitride, tantalum or tantalum nitride, patterned multi-stack material layers containing or consisting of stacks e.g. of alternating polysilicon and silicon dioxide layers, and patterned dielectric material layers containing or consisting of silicon dioxide or low-k or ultra-low-k dielectric materials are produced by photolithographic techniques. Nowadays, such patterned material layers comprise structures of dimensions even below 22 nm with high aspect ratios.
Photolithography is a method in which a pattern on a mask is projected onto a substrate such as a semiconductor wafer. Semiconductor photolithography typically includes the step of applying a layer of a photoresist on a top surface of the semiconductor substrate and exposing the photoresist to actinic radiation, in particular UV radiation of a wavelength of, for example, 193 nm, through the mask. In order to extend the 193 nm photolithography to the 22 nm and the 15 nm technology node, immersion photolithography has been developed as a resolution enhancement technique. In this technique, the air gap between the final lens of the optical system and the photoresist surface is replaced by a liquid medium that has a refractive index greater than one, e.g., ultra pure water with a refractive index of 1.44 for the wavelength of 193 nm. However, in order to avoid leaching, water-uptake and pattern degradation, a barrier coating or a water resistant photoresist must be used. These measures however add to the complexity of the manufacturing process and are therefore disadvantageous.
Beside the 193 nm-immersion lithography other illumination techniques with significant shorter wavelength are considered to be solutions to fulfil the needs of further downscaling of the to be printed feature sizes of 20 nm node and below. Beside e-Beam exposure the Extreme Ultraviolet (EUV) Lithography with a wavelength of approx. 13.5 nm seem to be the most promising candidate to replace immersion lithography in the future. After exposure the subsequent process flow is quite similar for immersion and EUV lithography.
An optional post-exposure bake (PEB) is often performed to allow the exposed photoresist polymers to cleave. The substrate including the cleaved polymer photoresist is then transferred to a developing chamber to remove the exposed photoresist, which is soluble in aqueous developing compositions. Typically, such developing compositions comprise tetraalkylammonium hydroxides, such as but not limited to tetramethylammonium hydroxide (TMAH) are applied to the resist surface in the form of a puddle to develop the exposed photoresist. A deionized water rinse is then applied to the substrate to remove the dissolved polymers of the photoresists. The substrate is then sent to a spin drying process. Thereafter, the substrate can be transferred to the next process step, which may include a hard bake process to remove any moisture from the photoresist surface.
Irrespective of the exposure techniques the wet chemical processing of small patterns however involves a plurality of problems. As technologies advance and dimension requirements become stricter and stricter, photoresist patterns are required to include relatively thin and tall structures or features of photoresists, i.e., features having a high aspect ratio, on the substrate. These structures may suffer from bending and/or collapsing (so called pattern collapse), in particular, during the spin dry process, due to excessive capillary forces of the liquid or solution of the rinsing liquid deionized water remaining from the chemical rinse and spin dry processes and being disposed between adjacent photoresist features. The calculated maximum stress σ between small features caused by the capillary forces can be described according to Namatsu et al. Appl. Phys. Lett. 66(20), 1995 as follows:
  σ  =                              6          ·          γ          ·          cos                ⁢                                  ⁢        θ            D        ·                  (                  H          W                )            2      wherein γ is the surface tension of the fluid, θ is the contact angle of the fluid on the feature material surface, D is the distance between the features, H is the height of the features, and W is the width of the features.
To lower the maximum stress, generally the following approaches exist:    (a) lower the surface tension γ of the fluid,    (b) lower the contact angle of the fluid on the feature material surface.
In another approach to lower the maximum stress σ for immersion lithography may include using a photoresist with modified polymers to make it more hydrophobic. However, this solution may decrease the wettability of the developing solution.
Another problem of the conventional photolithographic process is line edge roughness (LER) and line width roughness (LWR) due to resist and optical resolution limits. LER includes horizontal and vertical deviations from the feature's ideal form. Especially as critical dimensions shrink, the LER and LWR become more problematic and may cause yield loss in the manufacturing process of IC devices.
Due to the shrinkage of the dimensions, the removal of particles in order to achieve a defect reduction becomes also a critical factor. This does not only apply to photoresist patterns but also to other patterned material layers, which are generated during the manufacture of optical devices, micromachines and mechanical precision devices.
An additional problem of the conventional photolithographic process is the presence of watermark defects. Watermarks may form on the photoresist as the deionized water or rinse liquid cannot be spun off from the hydrophobic surface of the photoresist. The photoresist may be hydrophobic particularly in areas of isolated, or non-dense, patterning. The watermarks have a harmful effect on yield and IC device performance.
However, besides the rinsing/cleaning step described above, also the swelling of the photoresist in the photoresist developing step may increase the risk of pattern collapse and should therefore be avoided.
EP 1 553 454 A2 discloses the use of cetylmethylammonium, stearylmethylammonium, cetyltrimethylammonium, stearyltrimethylammonium, distearyldimethylammonium, stearyldimethylbenzylammoium, dodecylmethylammonium, dodecyltrimethylammonium, benzylmethylammonium, benzyltrimethylammonium, and benzalkonium chloride as cationic surfactants in rinsing compositions for patterns having line-space dimensions of 90 nm.
U.S. Pat. No. 6,670,107 B2 discloses a method for the reduction of defects in an electronic device comprising of cationic and non-ionic surfactants in concentration less than or equal to the critical micelle concentration. US 2010/0248164 A1 discloses a rinse solution for preventing pattern collapse consisting of an anionic surfactant, an amine and water.
Patent application US 2000/53172 A1 discloses that the acetylenic diol-type of surfactant solutions prevent pattern collapse by making the surface of a photoresist hydrophilic thus improving the wettability of the rinse or solution.
In summary, pattern collapse may generally be caused by:    A. Swelling of the photoresist in the developing phase,    B. Capillary action of the rinsing/cleaning composition during the liquid spin-off at the end of the rinse,    C. Poor adhesion of the patterned structures to the underlayer,    D. Material incompatibility leading to swelling and weakening of the structures.
The present invention mainly addresses the problems under Lit. A and B, i.e. to prevent swelling of the photoresist and to prevent pattern collapse by using a defect reduction rinse after the development of the photoresist.
It is therefore an object of the present invention to provide a method for manufacturing integrated circuits for nodes of 50 nm and lower, in particular for nodes of 32 nm and lower and, especially, for nodes of 22 nm and lower, which method no longer exhibits the disadvantages of prior art manufacturing methods.
In particular, the compounds according to the present invention shall allow for    the immersion photolithography of photoresist layers,    the developing of the photoresist layers exposed to actinic radiation through a mask,    the chemical rinse of patterned material layers    comprising patterns with a high aspect ratio and line-space dimensions of 50 nm and less, in particular, of 32 nm and less, especially, of 22 nm and less, without causing pattern collapse, an increase of LER, LWR and watermark defects.
The components according to the present invention should allow for a significant reduction of LER and LWR by smoothing the roughness of the surfaces of the developed photoresist patterns. It should also allow for the efficient prevention and/or the removal of watermark defects on patterned material layers, in particular, but not limited to photoresist patterns. Furthermore it should allow for the efficient removal of particles in order to achieve a significant defect reduction on patterned material layers.
The components according to the present invention should also allow for a significant reduction of photoresist swelling.